This invention relates to a device for recovering vapor generated in a closed system for dispensing volatile liquids, such as gasoline from a tank generally stalled under the ground to a vehicle fuel tank.
The amount of generated vapor is varied depending on a difference of a temperature of liquid, such as gasoline stored in the underground tank to be supplied, from an ambient temperature above the ground surface, and how far gasoline is agitated through the pump and nozzle, and splashed into the vehicle tank. When the vapor amount in the vehicle tank comes to be so much, the vapor is bursted out of a gap formed between a nozzle outer surface and a fuel filler pipe, which may result in dangerous problem. Even if the vapor amount does not reach the level referred to above, ordinarily released vapor causes air pollution and lead to useless loss of valuable energy.
Thus, vapor is usually recovered so as to be forcibly returned in the supply tank. For instance, U.S. Pat. No. 3,850,208 discloses a gun nozzle for supplying fuel to a vehicle such as automobile, which comprises a pair of independent passages to be connected respectively with a gasoline duct and a vapor duct of the gasoline dispensing apparatus, as well as two cavities eccentrically shaped and diametrically opposed across a central rotor, which has a plurality of radial slots and a corresponding number of vanes each yieldingly projecting from the concerned slot so as to seal the inner wall of the cavities, whereby when gasoline forcedly flows through the gasoline passage, the rotor is turned so as to feed vapor in the opposite direction to the vapor conduit.
Since the gun nozzle contains such liquid motor and vapor pump therein, the size and weight thereof is too large and heavy to readily handle. Furthermore, due to that liquid is apt to leak into the vapor pumping cavity in view of the constructional nature, the metered volume of gasoline often comes to be not correct. In view of such particular construction of the vapor pump, moreover, it is difficult to recover a large amount of vapor to be released for instance when the ambient temperature is considerably high.
In order to avoid and overcome the defects referred to above, U.S. Pat. No. 4,068,687 proposes a vapor recovery device comprising a hydraulic motor to be driven by the force of flowing liquid such as supplied gasoline as well as a pneumatic pump of a larger capacity than that of the motor. The pump for vapor is provided separately from the motor different from the above but the both are drivingly connected together by a common shaft so that the vapor pump is driven by the motor similar to the above. Owing to the larger capacity of the pump, a fairly large amount of vapor can be recovered, but when the amount of vapor generated is more than the rated capacity, it is impossible to recover such excessive vapor.
Furthermore, since the pump is stopped directly when fuel supply is stopped, vapor is to remain in the vapor recovery duct to flow out in the atmosphere.